Delayed gelation polymer system for high temperature and high salinity applications

Abstract

This disclosure describes the composition and methods of use for a novel delayed polymer gelation system for high temperature and high salinity applications. This polymer gelation system includes a polymer of acrylamide, AMPS and 500-5000 ppm polyethylene glycol diacrylate in inverse emulsion form, and a polyethyleneimine (PEI) with a MW of 2,000-30,000 daltons as the crosslinking agent.

What is claimed is: 
     
       1. A polymer system comprising:
 a polymer comprising:
 acrylamide; 
 2-acrylamido-2-methylpropane sulfonic acid (AMPS); 
 polyethylene glycol diacrylate; and 
 sodium formate; 
 
 a crosslinker comprising polyethyleneimine; and 
 a temperature stabilizer; 
 wherein the polymer is in inverse emulsion form. 
 
     
     
       2. The polymer system of  claim 1  wherein the polymer is at a concentration of about 25-35%. 
     
     
       3. The polymer system of  claim 1  wherein the polymer comprises:
 about 50-90% acrylamide; 
 about 10-50% AMPS; 
 about 500-5000 ppm polyethylene glycol diacrylate; and 
 about 100-2000 ppm sodium formate; 
 wherein the crosslinker comprises about 100-1500 ppm polyethyleneimine. 
 
     
     
       4. The polymer system of  claim 3  wherein the polymer comprises:
 about 80% acrylamide; 
 about 20% AMPS; 
 about 500 ppm polyethylene glycol diacrylate; and 
 about 400 ppm sodium formate; 
 wherein the crosslinker comprises about 1200 ppm polyethyleneimine. 
 
     
     
       5. The polymer system of  claim 3  wherein the polymer comprises:
 about 60% acrylamide; 
 about 40% AMPS; 
 about 500 ppm polyethylene glycol diacrylate; and 
 about 400 ppm sodium formate; 
 wherein the crosslinker comprises about 200 ppm polyethyleneimine. 
 
     
     
       6. The polymer system of  claim 1  wherein the crosslinker comprises polyethyleneimine at a molecular weight of about 2,000-30,000 daltons. 
     
     
       7. The polymer system of  claim 6  wherein the polyethyleneimine has a molecular weight of about 10,000 daltons. 
     
     
       8. The polymer system of  claim 1  wherein the temperature stabilizer comprises about 0.02-0.1 wt % thiourea. 
     
     
       9. The polymer system of  claim 1  wherein the viscosity of the polymer system is about 1-10 cp before gelation. 
     
     
       10. The polymer system of  claim 1  wherein the polymer system undergoes gelation at a temperature between about 80-130 degrees Celsius and wherein the polymer gel is formed in a brine with total dissolved solids in the range of about 50,000 mg/L to 200,000 mg/L. 
     
     
       11. A method of improving sweep efficiency for an oil-bearing zone comprising:
 preparing a polymer system comprising:
 a polymer comprising:
 acrylamide; 
 2-acrylamido-2-methylpropane sulfonic acid (AMPS); 
 polyethylene glycol diacrylate; and 
 sodium formate; 
 
 a crosslinker comprising polyethyleneimine; and 
 a temperature stabilizer; 
 wherein the polymer is in inverse emulsion form; and 
 
 injecting the polymer system into a wellbore to improve the sweep efficiency. 
 
     
     
       12. The method of  claim 11  wherein the polymer is at a concentration of about 25-35% in the inverse emulsion. 
     
     
       13. The method of  claim 11  wherein the polymer comprises
 about 50-90% acrylamide; 
 about 10-50% AMPS; 
 about 500-5000 ppm polyethylene glycol diacrylate; and 
 about 100-2000 ppm sodium formate; 
 wherein the crosslinker comprises about 100-1500 ppm polyethyleneimine. 
 
     
     
       14. The method of  claim 13  wherein the polymer comprises
 about 80% acrylamide; 
 about 20% AMPS; 
 about 500 ppm polyethylene glycol diacrylate; and 
 about 400 ppm sodium formate; 
 wherein the crosslinker comprises about 1200 ppm polyethyleneimine. 
 
     
     
       15. The method of  claim 13  wherein the polymer comprises
 about 60% acrylamide; 
 about 40% AMPS; 
 about 500 ppm polyethylene glycol diacrylate; and 
 about 400 ppm sodium formate; 
 wherein the crosslinker comprises about 200 ppm polyethyleneimine. 
 
     
     
       16. The method of  claim 11  wherein the crosslinker comprises polyethyleneimine at a molecular weight of about 2,000-30,000 daltons. 
     
     
       17. The method of  claim 16  wherein the polyethyleneimine has a molecular weight of about 10,000 daltons. 
     
     
       18. The method of  claim 11  wherein the temperature stabilizer comprises about 0.02-0.1 wt % thiourea. 
     
     
       19. The method of  claim 11  wherein the viscosity of the polymer system is about 1-10 cp before gelation. 
     
     
       20. The method of  claim 11  wherein the polymer system undergoes gelation at a temperature between about 80-130 degrees Celsius and wherein the polymer gel is formed in a brine with total dissolved solids in the range of about 50,000 mg/L to 200,000 mg/L.